The present invention relates to the art of data networks. More particularly, the present invention relates to data networks using optical switches.
Because of ever increasing bandwidth requirements, data networks utilizing optical transmission systems are becoming popular. Optical transmission systems have a larger bandwidth compared to electrical transmission systems.
FIG. 1 illustrates a simplified optical switching network 100 including a plurality of input lines represented by lines 102a, 102b, and ellipsis 102c (collectively, “102”) and a plurality of output lines represented by lines 104a, 104b, and ellipsis 104c (collectively, “104”). In the network 100, three optical nodes NA 110, NB 120, and NC 130 are illustrated. Although only three nodes are shown, the switching network 100 may include hundreds or even thousands of interconnected optical nodes.
Node NA 110 has an optical switch 112, a control circuit 114, and a plurality of input lines and output lines, or ports, designated, for convenience, NA0 to NAn where n is an integer. Typical values for n may be 15, 63, or 255. The ports—NA0, NA1, . . . and NAn—are ports of the node NA 110 as well as the ports of the switch 112. The switch 112 may utilize micro mirrors, liquid, or gaseous elements (generically, “switching element”) to direct or reflect optical signals from a first port to a second port. Typically, the ports are bi-directional but is sometimes uni-directional. The control circuit 114, connected to the switch 112, controls the state of the switching elements to implement Node NA 110 as described herein above is known in the art.
Nodes NB 120 and NC 130 are similarly configured to node NA 110, and their ports are similarly denoted herein. A path router 140 is connected to nodes NA 110, NB 120, and NC 130. The path router 140 contains physical path topology of the network 100 necessary to make connections as requested. The path router 140 contains the physical network topology of how the switches are connected.
For instance, in order for the path router 140 to successfully direct an input signal at input line 102b to an output line 104b, the path router 140 needs to know that (1) the input line 102b feeds into port NA1; (2) port NA9 is connected to port NB1; (3 port) NB8 is connected to port NC7; and (4) port NC9 is connected to the output line 104b. With the information, the path router 140 signals node NA 110 to route its port NA1 to its port NA9, signals node NB 120 to link its port NB1 to its port NB8, and signals node NC 130 to link its port NC7 to its port NC9. The physical path topology information may be entered directly into the path router 140 or supplied by an external controller system (not shown), connected to the path router 140.
In the illustrated configuration, port NA9 is connected to port NB1 (connection 150) and port NB8 is connected to port NC7 (connection 152). The other ports of nodes NA 110, NB 120, and NC 130 may be connected to ports of nodes not show in FIG. 1. As the number of nodes, thus the ports, grows in the network 100, the number of possible connections grows exponentially. It is not uncommon to have a network with hundreds or even thousands of ports. Prior art requires that the physical topology be configured manually.
Without a correct topology of the network 100 as defined by the connection information of the routing table, the network 100 does not operate effectively.
The processes of manually defining the full network physical path topology for the path router 140 are susceptible to error. For example, an optical path can be made to an unintended port or to an unintended node. Or, incorrect data may be entered into the path router 140. The problem is exacerbated by the fact that networks are becoming increasingly large and complex.
Moreover, when new nodes are installed, connections are modified, or when error in connection information is suspected, the entire network must be manually analyzed, and the topology manually reconfigured. No dynamic or automated procedure exists to determine the network topology.
Accordingly, there remains a need for an improved technique to determine the connections and topology of an optical network.